netdev - [PATCH v2 net-next 3/3] bonding: fix __get_active

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Message-Id: <1389266425-28365-4-git-send-email-vfalico@redhat.com>
Date:	Thu,  9 Jan 2014 12:20:25 +0100
From:	Veaceslav Falico <vfalico@...hat.com>
To:	netdev@...r.kernel.org
Cc:	Veaceslav Falico <vfalico@...hat.com>, dingtianhong@...wei.com,
	Jay Vosburgh <fubar@...ibm.com>,
	Andy Gospodarek <andy@...yhouse.net>
Subject: [PATCH v2 net-next 3/3] bonding: fix __get_active_agg() RCU logic

Currently, the implementation is meaningless - once again, we take the
slave structure and use it after we've exited RCU critical section.

Fix this by removing the rcu_read_lock() from __get_active_agg(), and
ensuring that all its callers are holding either RCU or RTNL lock.

Fixes: be79bd048 ("bonding: add RCU for bond_3ad_state_machine_handler()")
CC: dingtianhong@...wei.com
CC: Jay Vosburgh <fubar@...ibm.com>
CC: Andy Gospodarek <andy@...yhouse.net>
Signed-off-by: Veaceslav Falico <vfalico@...hat.com>
---

Notes:
    v1 -> v2:
    Don't use RCU primitives as we can hold RTNL.

 drivers/net/bonding/bond_3ad.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
index d2782c8..845545b 100644
--- a/drivers/net/bonding/bond_3ad.c
+++ b/drivers/net/bonding/bond_3ad.c
@@ -674,6 +674,8 @@ static u32 __get_agg_bandwidth(struct aggregator *aggregator)
 /**
  * __get_active_agg - get the current active aggregator
  * @aggregator: the aggregator we're looking at
+ *
+ * Caller must hold either RCU or RTNL lock.
  */
 static struct aggregator *__get_active_agg(struct aggregator *aggregator)
 {
@@ -681,13 +683,9 @@ static struct aggregator *__get_active_agg(struct aggregator *aggregator)
 	struct list_head *iter;
 	struct slave *slave;
 
-	rcu_read_lock();
-	bond_for_each_slave_rcu(bond, slave, iter)
-		if (SLAVE_AD_INFO(slave).aggregator.is_active) {
-			rcu_read_unlock();
+	bond_for_each_slave(bond, slave, iter)
+		if (SLAVE_AD_INFO(slave).aggregator.is_active)
 			return &(SLAVE_AD_INFO(slave).aggregator);
-		}
-	rcu_read_unlock();
 
 	return NULL;
 }
@@ -1495,11 +1493,11 @@ static void ad_agg_selection_logic(struct aggregator *agg)
 	struct slave *slave;
 	struct port *port;
 
+	rcu_read_lock();
 	origin = agg;
 	active = __get_active_agg(agg);
 	best = (active && agg_device_up(active)) ? active : NULL;
 
-	rcu_read_lock();
 	bond_for_each_slave_rcu(bond, slave, iter) {
 		agg = &(SLAVE_AD_INFO(slave).aggregator);
 
-- 
1.8.4

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